Characterization of polycrystalline Cu(In,Ga)Te2 thin films prepared by pulsed laser deposition

Thin films of the chalcopyrite compound CuGaXIn1-XTe2 (0=<X=<1) have been prepared by pulsed laser deposition (PLD) of prereacted material onto glass substrates. The structural and optical properties of these films have been investigated using the techniques of X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), Rutherford back scattering (RBS), transmittance (T), reflectance (R). Electrical characterization was performed using Hall and resistivity measurements, using the Van der Pauw technique at 300 K. The composition of the laser-deposited films was found to closely match that of the target materials and the XRD showed them to be single phase with the chalcopyrite structure and a preferred orientation along the (112) plane. The spectral dependence of the refractive index n and absorption coefficient alpha of the Cu(In,Ga)Te2 thin films were determined using rigorous expressions for transmission and reflection in an air/film/substrate/air multilayer system. The CuGaXIn1-XTe2 films had optical absorption coefficients of order 104 cm-1 and the energy gaps observed in these films increased from 0.96 to 1.32 eV with increasing Ga content